- The stomach secretes a number of molecules which serve in both digestive and absorptive functions. Secretion of pepsinogen and stomach acid facilitate digestion of ingested foods and gastric mucus secretion protects the gastric mucosa from these powerful digestive fluids. Additionally, the gastric mucosa secretes Intrinsic Factor which is critical for absorption of Vitamin B12. Although the digestive functions of the stomach facilitate release of nutrients from food, the only secretory function of the stomach critical for life is synthesis and release of Intrinsic Factor. Because of its complex regulation, secretion of stomach acid is covered on its own page: Stomach Acid Secretion.
- Pepsinogen is a zymogen which auto-activates by self-cleaving into the powerful digestive protease pepsin when exposed to low pH environments. This mechanism ensures that pepsin is only active once fully secreted into the gastric lumen which possesses a sufficiently robust mucosal barrier that can prevent pepsin from digesting the mucosa. Pepsinogen is primarily secreted by the gastric chief cells of the oxyntic glands in response to stimulation either by the vagus nerve or the submucosal plexus. In addition, presence of acid within the stomach stimulates pepsinogen secretion likely via local reflexes conducted by the enteric nervous system.
- Mucus is secreted by the mucous neck cells of the oxyntic glands and pyloric glands as well as gastric epithelial mucous cells. These create a thick layer of mucous which protects the gastric mucosa from the actions of pepsin and stomach acid.
|Intrinsic Factor Secretion|
- Secretion of intrinsic factor is performed by the parietal cells located in gastric oxyntic glands. The role of intrinsic factor in Vitamin B12 resorption will be added later under a "Vitamin B12" page.